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Perovskite type

As compared to the ReOs-type the cubic perovskite AMeFs contains an additional ion A in the center of the unit cell. The vacancies in the cubic close-packing of anions are thus filled up by insertion of similar sized cations A that complete the layers (111) to have the composition AF . [Pg.41]

1 The ionic radii for calculation of the tolerance factor t have been taken from Ahrens (2). An increase of 6% has been taken into account for the A-ions in 12-coordination (246). Only the Me + ionic radii of Zn and Cd were slightly modified, as indicated by the molecular volumes of their compounds relative to others (rzn = 0.71 A, red = 0.86 A, instead of 0.74 and 0.97 A resp.). By similar reasons, the ionic radii of both, NHj+ and T1+ were enlarged as compared to that of Rb+ (1.47 A) (riiH4 = 1-48 A, rn = 1.49 A, instead of 1.43 and 1.47.A resp.). A fluoride ionic radius of rj- = 1.33 A has been accepted. [Pg.41]

The A-ions become 12-coordinated thereby there are 6 F in the same plane and twice 3 F more in the neighbouring ones, all at equal distances of A-F = a/y2. [Pg.42]

The Me ions at the comers of the unit cell occupy the octahedral holes with Me—F-distances of /2. All MeFe-octahedra are sharing corners and form a three-dimensional linear framework, the smallest cell of which is the cubic unit cell itself. [Pg.42]

The two mentioned ternary fluorides of cadmium with their tolerance factors of 1.00 and 0.88 resp. mark quite accurately the field of existence of cubic perovskites. As may be seen from the following Table 25 the tolerance factors of all cubic fluoroperovskites of the transition metals hitherto known lie within the range of these limits. [Pg.42]


Fig. 2. Cubic (m3m) prototype stmcture of perovskite-type ABO compounds where , A , B and O, O. Fig. 2. Cubic (m3m) prototype stmcture of perovskite-type ABO compounds where , A , B and O, O.
Perovskite-type compounds, especially BaTiO, have the abiUty to form extensive soHd solutions. By this means a wide variety of materials having continuously changing electrical properties can be produced ia the polycrystaUine ceramic state. By substituting ions for ions, T can be... [Pg.204]

Recent applications of e-beam and HF-plasma SNMS have been published in the following areas aerosol particles [3.77], X-ray mirrors [3.78, 3.79], ceramics and hard coatings [3.80-3.84], glasses [3.85], interface reactions [3.86], ion implantations [3.87], molecular beam epitaxy (MBE) layers [3.88], multilayer systems [3.89], ohmic contacts [3.90], organic additives [3.91], perovskite-type and superconducting layers [3.92], steel [3.93, 3.94], surface deposition [3.95], sub-surface diffusion [3.96], sensors [3.97-3.99], soil [3.100], and thermal barrier coatings [3.101]. [Pg.131]

Properties and Applications of Perovskite-Type Oxides, edited by L. G. Tejuca and J. L. G. Fierro... [Pg.674]

By heating the metal with appropriate oxides or carbonates of alkali or alkaline earth metals, a number of mixed oxides of Ru and Os have been made. They include NasOs Og, LifiOs Og and the ruthenites , M Ru 03, in all of which the metal is situated in octahedral sites of an oxide lattice. Ru (octahedral) has now also been established by Ru Mdssbauer spectroscopy as a common stable oxidation state in mixed oxides such as Na3Ru 04, Na4Ru2 07, and the ordered perovskite-type phases M Ln Ru Og. [Pg.1082]

When 0.4 < x < 0.53, an orthorhombic phase is observed in the AgxNb02+xFi.x system. This phase undergoes a phase transition at 900°C that leads to the formation of a tetragonal phase, which crystallizes in a tetragonal tungsten bronze-type structure with cell parameters a = 12.343 and c = 3.905 A. When 0.82 < x < 1, solid solutions based on AgNb03 were found, which crystallize in a perovskite-type structure. [Pg.103]

Lithium dioxyfluoroniobate (IV), LiNb02F, also has a LiNb03-type crystal structure, while dioxyfluoroniobates of sodium and potassium, NaNb02F and KNb02F, crystallize in a perovskite-type structure [247]. [Pg.104]

The structure of the perovskite-type lithium ion conductor Li0 29La0 57Ti03 is represented in Fig. 6. The small gray circles depict the lithium ions, the big gray circles the lanthanum ions. These are randomly distributed over the A sites 14 per-... [Pg.527]

Figure 6. Structure of the perovskite-type lithium-ion conductor Li 2yLa057TiO3. The lithium ions (small, gray) and the lanthanum ions (large, gray) are randomly distributed over the A sites, of which 14 percent are vacancies, enabling the lithium ions to be mobile. Titanium forms TiOh octahedra, as shown in yellow. The unit cell is indicated. Figure 6. Structure of the perovskite-type lithium-ion conductor Li 2yLa057TiO3. The lithium ions (small, gray) and the lanthanum ions (large, gray) are randomly distributed over the A sites, of which 14 percent are vacancies, enabling the lithium ions to be mobile. Titanium forms TiOh octahedra, as shown in yellow. The unit cell is indicated.
Catalytic removal of diesel soot particulates over LaMnOs perovskite-type oxides... [Pg.261]

Catalytic combustion of diesel soot particulates over LaMnOs perovskite-type oxides prepared by malic acid method has been studied. In the LaMn03 catalyst, the partial substitution of alkali metal ions into A site enhanced the catalytic activity in the combustion of diesel soot particulates and the activity was shown in following order Cs>K>Na. In the LarxCs MnOj catalyst, the catalytic activity increased with an increase of X value and showed constant activity at the substitution of x>0.3... [Pg.261]

Several researchers have focused their attention on the application of oxide materials to lower the oxidation temperature of soot particulates. It was reported that active soot oxidation catalysts are PbO, C03O4, V2O5, M0O3, CuO, and perovskite type oxides[3]. [Pg.261]

In this paper, we prepared LaMnOa perovskite-type oxides using the malic acid method and investigated their physical properties. It has been also investigated the effect of partial substitution of metal iorrs into La and Mn sites and the reaction conditions on the activity for the combustion of soot particulates. [Pg.261]

The preparation method of perovskite-type oxides was taken from the previous paper[4]. Malic acid was added into mixed aqueous solution of metal nitrates in a desired proportion so as for the molar ratio of malic... [Pg.261]

Table 1. Perovskite-type oxides prepared by malic acid method and their catalytic performances... Table 1. Perovskite-type oxides prepared by malic acid method and their catalytic performances...
Fig. 1. TG spectra of carbon particulates with Fig. 2. TPR profiles measured for various Lao.gCso MnOj catalyst heating rate=l K/min. perovskite type oxides heating rate=10 K/min,... Fig. 1. TG spectra of carbon particulates with Fig. 2. TPR profiles measured for various Lao.gCso MnOj catalyst heating rate=l K/min. perovskite type oxides heating rate=10 K/min,...
Fig. 2 shows the temperature as a function of irradiation time of Cu based material under microwave irradiation. CuO reached 792 K, whereas La2Cu04, CuTa20e and Cu-MOR gave only 325, 299 and 312 K, respectively. The performances of the perovskite type oxides were not very significant compared to the expectation from the paper reported by Will et al. [5]. This is probably because we used a single mode microwave oven whereas Will et al. employed multi-mode one. The multi-mode microwave oven is sometimes not very sensitive to sample s physical properties, such as electronic conductivity, crystal sizes. From the results by electric fixmace heating in Fig. 1, at least 400 K is necessary for NH3 removal. So, CuO was employed in the further experiments although other materials still reserve the possibility as active catalysts when we employ a multi-mode microwave oven. [Pg.311]

In perovskite-type catalysts the formation of the final phase is completed already at 973 K. XRD and skeletal FTIR/FTFIR data for LalCol, LalMnl and LalFel calcined at 973 K evidence that only LalFel-973 is actually monophasic and consists of a perovskite-type phase with orthorombic structure. A perovskite type phase with hexagonal-rombohedral structure represents the main phase of LalCol-973, but traces of C03O4 and La2C05 are also present. In the case of LalMnl-973 two phases have been detected both with perovskite-type structure, one orthorombic and the other rombohedral. The calculated cell parameters of the dominant perovskite-type phase are reported in Table 1 for the three samples. The results compare well with those reported in the literature [JCPDS 37-1493, 32-484, 25-1060] which refer to similar samples prepared via solid state reartion. All the perovskite-type samples are markedly sintered... [Pg.476]

In the case of H2 oxidation the two investigated classes of catalysts show different behaviors. Again perovskite type catalysts calcined at 973 K show higher combustion activity than hexaaluminates calcined at 1573 K, but characteristic values of parent activation energy (5-7 Kcal/mole) have been calculated for perovskite catalysts that are markedly lower than... [Pg.477]

An example for a compound of the perovskite type is LaNiOj. In other com-ponnds of the perovskite type, nickel may be replaced by cobalt or iron, and lan-thannm in part by alkaline-earth metals, an example being Lag 8Sro2Co03. The activity of perovskites toward cathodic oxygen reduction is low at room temperature but rises drastically with increasing temperature (particularly so above 150°C). In certain cases the activity rises so much that the equilibrium potential of the oxygen electrode is established. [Pg.545]

Among the high-temperature superconductors one finds various cuprates (i.e., ternary oxides of copper and barium) having a layered structure of the perovskite type, as well as more complicated oxides on the basis of copper oxide which also include oxides of yttrium, calcium, strontium, bismuth, thallium, and/or other metals. Today, all these oxide systems are studied closely by a variety of specialists, including physicists, chemists, physical chemists, and theoreticians attempting to elucidate the essence of this phenomenon. Studies of electrochemical aspects contribute markedly to progress in HTSCs. [Pg.630]

Superstructures of the perovskite type. Only in one octant have all atoms been plotted the atoms on the edges and in the centers of all octants are the same... [Pg.205]

Atoms of an element are substituted by atoms of another element that requires an altered kind of bonding. For example KMgF3 (perovskite type) -t CsGeCl3 (lone electron pair at the Ge atom, Ge atom shifted from the octahedron center towards an octahedron face so that the three covalent bonds of an GcCC ion are formed). [Pg.215]


See other pages where Perovskite type is mentioned: [Pg.346]    [Pg.57]    [Pg.58]    [Pg.386]    [Pg.681]    [Pg.103]    [Pg.538]    [Pg.95]    [Pg.264]    [Pg.309]    [Pg.421]    [Pg.473]    [Pg.475]    [Pg.478]    [Pg.483]    [Pg.430]    [Pg.434]    [Pg.57]    [Pg.170]    [Pg.172]    [Pg.202]    [Pg.204]   
See also in sourсe #XX -- [ Pg.50 ]




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Catalytic Performances of Perovskite-Type Catalysts for H2 Production from Alcohols

Complex perovskite-type oxide

Conductivity electric, perovskite-type oxides

Crystalline perovskite-type oxides

Cubic Perovskite-Type Structure

Electrolyte perovskite-type

Ionic Conduction in Perovskite-Type Compounds

Iron oxides perovskite-type

Mechanisms of Proton Conduction in Perovskite-Type Oxides

Mixed oxides, structure types perovskite

Oxidation catalysis over Perovskite-type

Oxide type perovskites

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Perovskite structure type example compounds

Perovskite type crystal

Perovskite type oxide catalysts

Perovskite type structure

Perovskite-type BaTiO

Perovskite-type Oxide Membranes for Air Separation

Perovskite-type Oxides Synthesis and Application in Catalysis

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Perovskite-type cathodes

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Perovskite-type metal oxides

Perovskite-type mixed-conducting

Perovskite-type mixed-conducting materials

Perovskite-type oxide structure

Perovskite-type oxides

Perovskite-type oxides ammonia oxidation

Perovskite-type oxides lanthanum-based catalysts

Perovskite-type oxides preparation

Perovskite-type oxides pressure

Perovskite-type oxides resistivity

Perovskite-type oxides sensors

Perovskite-type oxides, investigated under

Perovskite-type oxides, oxygen evolution

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